1. Field of the Invention
The present invention relates to sockets for below-knee prosthesis and more particularly to a socket that permits maximum necessary flexion while the prosthesis is secured to a residual limb.
2. Description of the Prior Art
Since the Middle Ages, sockets have provided a measure of protection for the residual limb of amputees, as well as a point of attachment for artificial limbs. Crude forerunners to the modern socket were constructed from iron or wood, which provided limited functionality and even less comfort. Advances in biomechanics and the development of materials such as moldable plastics and plastic laminates have dramatically improved the function and comfort of prosthetic sockets.
Although the modern transtibial, or below-knee, prosthesis can be found in a wide array of designs and configurations, the major components are typically the socket, a suspension system, a pylon and a foot system. As the primary point of contact between the residual limb and the prosthesis, the socket protects the residual limb and transmits the forces associated with standing and ambulation. Any relative motion between the residual limb and the socket oftentimes results in less than satisfactory ambulation and an increase in discomfort and fatigue. In order to obtain a precise fit, transtibial sockets are typically made by first creating a cast of the residual limb in a generally extended position. The cast is later filled with plaster or other molding material to create a positive model for a check socket. The prosthetist manually adjusts the check socket to compensate for any pressure points or bony protrusions. A second positive model of the residual limb is formed by filling the check socket with the molding material. The definitive socket is then prepared using the second positive model.
An increasing number of modern transtibial prosthetics are suspended using a suction suspension, such as hypobaric sleeves and silicone liners. Typical socket construction combined with such modern suspension systems oftentimes create a problem in easily or comfortably obtaining a normal range of motion. Most common socket designs provide a lower, flared posterior trim that is hand-fabricated by the prosthetist to allow for knee flexion. However, the flared posterior trim is typically inadequate to provide a normal range of motion due to the evolving shape of the individual's knee when the residual limb moves between full extension and plus ninety degrees flexion. Not only does the interaction between the rigid socket and the shape-changing knee cause discomfort and a limited range of motion, but it also applies pressure on the suspension system during periods of flexion, causing undo wear and tear on the prosthesis.
Accordingly, what is needed is a novel but simple method of making prosthetic sockets that permits maximum necessary flexion.